1. Field of the Invention
The present invention relates to a magnetic sensor apparatus having a Hall element disposed on a slant surface and a manufacturing method for the magnetic sensor apparatus.
2. Description of Related Art
A magnetic sensor apparatus having a Hall element disposed on a slant surface and a manufacturing method for the magnetic sensor apparatus are disclosed, for example, in pages 892 to 895 of “Transducers 93′, 1993 The 7th International Conference on Solid-State Sensors and Actuators” (Hereinafter, referred to as “Document 1”).
FIGS. 15A and 15B are schematic diagrams of the magnetic sensor apparatus 90 disclosed in the Document 1. FIG. 15A is a top view of the magnetic sensor apparatus 90, and FIG. 15B is a sectional view taken along line XVB-XVB in FIG. 15A.
The magnetic sensor apparatus 90 illustrated in FIGS. 15A and 15B has two Hall elements 2a and 2b. In the magnetic sensor apparatus 90, a deep recess it is formed by wet etching on a p-type silicon substrate 1, which has the {100} plane direction. The recess it is substantially square in its planer view and about 100 μm in depth. N-type low-concentration impurity diffusion regions 2a and 2b, which serve as the Hall elements, are formed on two slant surfaces of the silicon substrate 1, which have the {111} plane direction and are opposed to each other in the recess 1t. An n-type high-concentration impurity diffusion region 4 is formed as an electrode wiring connected to the Hall elements 2a and 2b. The section marked with numeral 3p in FIG. 15B is a polysilicon layer, which is a gate electrode used in the case where the low-concentration impurity diffusion regions (the Hall elements) 2a and 2b are used as transistors. In FIG. 15A, the graphic representation of the polysilicon layer 3p is omitted for the sake of simplicity, and only gate electrode wirings (electrical lines) Ga and Gb are shown.
With reference to FIG. 15B, in the magnetic sensor apparatus 90, when a magnetic field Bo, which is directed parallel to the plane of the XVB-XVB section of FIG. 15A, is applied, magnetic field components Ba and Bb, which are directed perpendicular to the slant surfaces, respectively, are applied to the respective Hall elements 2a and 2b. In the Hall elements 2a and 2b, through which bias currents Ia and Ib are passed, the voltages, which are proportional to the magnetic field components Ba and Bb (Hall voltages), are produced. The Hall voltages are detected as output voltages Va and Vb. Thus, for example, the rotational angle of the magnetic field Bo, which rotates in the plane of the XVB-XVB section, can be detected based on the output voltages Va and Vb and the two signals, which are different in phase, throughout the 360 degree range. Therefore, the magnetic sensor apparatus 90 can be used as a rotational angle sensor.
Another magnetic sensor apparatus having a Hall element disposed perpendicularly to the substrate face and a manufacturing method for the magnetic sensor apparatus are disclosed in pages 212 to 215 of IEEJ Transactions on Sensors and Micromachines, Vol. 122, No. 4 (2002) (Hereinafter, referred to as “Document 2”).
FIG. 16 is a schematic sectional view of the magnetic sensor apparatus 91 disclosed in the Document 2.
In the magnetic sensor apparatus 91 illustrated in FIG. 16, two silicon substrates 1a and 1b are used. The Hall element 2c of the magnetic sensor apparatus 91 is formed over a n-type silicon substrate 1a. A recess 1as is formed in the silicon substrate 1a around the Hall element 2c. The Hall element forming arrangement 2ck, which includes the Hall element 2c, is provided by the following procedure. That is, a metal layer 6 and a resin layer 7 laminated over the silicon substrate 1a are bent at the junction B, encircled with an alternate long and short dash line in FIG. 16. The metal layer 6 and the resin layer 7 are then folded upward. Another silicon substrate 1b is joined to the silicon substrate 1a in proximity to the Hall element forming arrangement 2ck at the bonding portion C encircled with an alternate long and short dash line in the figure. The Hall element forming arrangement 2ck is bonded to the perpendicular wall face 1bw provided by the silicon substrate 1b, and held there. The metal layer 6 is composed of a laminate of chromium (Cr)/gold (Au), and the resin layer 7 is composed of polyimide. The area marked with numeral 5 in FIG. 16 is a dielectric insulating layer.
With respect to the magnetic sensor apparatus 90 in FIGS. 15A and 15B, patterning of a resist is required for forming the low-concentration impurity diffusion regions 2a and 2b as the Hall elements and the high-concentration impurity diffusion region 4 as the electrode wiring. However, there are disadvantages. Specifically, the diffusion regions 2a, 2b, and 4 are formed across the slant surfaces of the recess 1t that is as deep as 100 μm or so. Therefore, an electron beam (EB) lithography technology in which a large focal range is obtained must be used. Even when an electron beam large in focal range is used, the single exposure is insufficient, and electron beam exposure must be carried out in four stages at different focal depths. For this reason, this method for the manufacture of the magnetic sensor apparatus 90 requires much processing time and gives poor throughput (several pieces/hour). Thus, this method is unsuitable for mass production.
The magnetic sensor apparatus 91 in FIG. 16 has another disadvantage. The silicon substrate 1b is protruded upward from the silicon substrate 1a at the bonding portion C in the figure, and this increases the size of the magnetic sensor apparatus 91 itself. In processing the perpendicular wall face 1bw of the silicon substrate 1b, cutting by dicing and planarization by thermal oxidation after the dicing and oxide layer removal are used. However, thermal oxidation and planarization by oxide layer removal must be repeatedly carried out, and this increases processing time. In dicing, an error is prone to be produced in the formation angle of the wall face 1bw. When there is an error in the formation angle of the wall face 1bw, information obtained from the Hall element 2c also has an error.